Biotin is an essential component for all living organisms even though many, including humans, cannot synthesize biotin and are dependent upon its uptake from their environment or diet (Eisenberg (1973) Adv Enzymol 38:317-372, Pai (1975) J Bacteriol 121:1-8). Biotin serves as a cofactor that covalently binds to carboxylases and facilitates the transfer of carboxyl groups during enzymatic reactions involving carboxylation, decarboxylation and transcarboxylation (Dakshinamurti and Bhagavan, eds., (1985) “Biotin ”, Ann NY Acad Sci 447:1-441; Knowles (1989) Ann Rev Biochem 58:195-221).
Biotin biosynthesis has been extensively studied in microorganisms, using biotin auxotrophic mutants to characterize the pathway. The biosynthesis of biotin involves four enzymatic steps in all microorganisms that starts with the precursor pimeloyl-CoA. The final step in this pathway involves the addition of sulfur to desthiobiotin to form biotin. The enzyme responsible for this reaction is known as biotin synthase and is encoded by the bioB gene (Birch et al. (1995) J Biol Chem 270:19158-19165).
The biotin biosynthetic pathway in plant cells has also been elucidated biochemically (Baldet (1993) Eur J Biochem 217:479-485) and genetically (Patton et al. (1998) Plant Physiol 116:935-946. This pathway is very similar to the bacterial pathways. Recent work has shown that increasing the level of biotin synthase activity in cells can direct the production of more biotin (U.S. Pat. No. 5,859,335 and 5,869,719). The present invention describes the identification of several new plant genes encoding biotin synthase. The use of these genes in plants as targets for herbicide treatment is disclosed.